Question

Which of the following is not correct for the ionic crystals?
(a) They possess a high melting point and boiling point.
(b) All are electrolytes.
(c) Exhibit the property of isomorphism.
(d) Exhibit directional properties of the bond.

Answer 1

Hint: In Ionic crystals the oppositely charged ions i.e., cations and anions are held together by a strong electrostatic force of attraction e.g.,\[NaCl\] and \[KCl\].

Complete Step by Step Solution:
The ionic crystals are formed by the transfer of electrons from less electronegative to more electronegative atoms as a result the formation of ions occurs.
In the ionic crystal, the atom which donates its electrons has a positive charge whereas the atom which gains electrons has a negative charge.
There is an electrostatic force of attraction found between the oppositely charged ions. This electrostatic force considers an ionic bond.
Because ionic compounds possess a strong electrostatic force of attraction, therefore, they have very high melting, boiling points, and high enthalpies of fusion vaporisation.
Due to the presence of a strong electrostatic force of attraction in solid-state, they do not conduct electricity (act as an insulator). Whereas, in a molten state, they are good conductors of electricity due to the possible movement of ions.
The ionic crystals are soluble in water and insoluble in organic solvents such as ether, hexane, benzene, etc.
The ionic crystals also exhibit isomorphism. In isomorphism two or more substances possess a similar crystal structure.
The ionic crystals are non-directional in nature i.e., in these crystals no overlapping of orbitals takes place and the oppositely charged ion is held together by a strong electrostatic force of attraction.
 Therefore, from the above explanation, option (d) will be the correct answer.

Note: The ionic bond is formed when the donor atom and the acceptor atom want to gain an inert noble gas configuration to complete their octet. Unlike a covalent bond, the complete transfer of electrons takes place in an ionic bond.